This invention relates to apparatus which produces a highly noticeable, useful and quickly remarked-upon appearance of depth or three-dimensionality when applied to a television screen, a motion picture screen or single still slide projections or pictures, or the like. The invention does not depend upon stereoscopic methods (a separate picture for each eye) and it employs apparatus at the screen rather than at the eyes. Hence, it is suitable for simultaneous viewing by several people or large audiences.
This invention comes in part from recognizing that stereopsis (the total process involving two eyes and the nerve connections and brain mechanism trained to interpret slight differences between the two pictures as indicating depth or three-dimensionality) is not the only clue to three-dimensional vision. Quite the contrary, at least ten other clues exist and will be detailed later. This invention is based on properly suppressing stereoptic and other information which indicates that the picture is flat, and allowing other clues to come forward to construct an appearance of depth which the brain readily accepts. A case in point is that if an observer closes one eye and looks at the world with the other, after a few moments the world looks three-dimensional, possessed of depth, and very obviously not any thing like a flat picture; yet no stereopsis is taking place, since with one eye, no stereoscopic clues are present.
Before describing the invention and the principles on which it is believed to work, both the successes and the still enormous problems of the stereoscopic approach will first be discussed as necessary background to the usefulness and need for this invention.
The use of stereopsis to provide a depth illusion from two-dimensional pictures has resulted in many means, over the years, to provide each eye with a slightly different picture (usually pictures taken from positions a few inches apart horizontally, corresponsing to the spacing between the eyes). The greatest ingenuity has been exercised to get these pictures to be seen separately by each eye. To this end, many techniques have been used, starting with the old-fashioned stereoscope with two lenses and a septum to help the observer combine the two pictures and yet prevent each eye from seeing both pictures. A version of this is used to this day with 3-D viewers for looking at transparencies, or in the commercially available stereo picture sets called Viewmaster. These have been very successful.
The real difficulty arises, however, when a three-dimensional effect is desired to be shown to an audience of many people, or even a few people simultaneously. Then the problem of getting a different picture to each eye of each observer becomes formidable and no commercially successful device has appeared.
To solve this problem, one of the earliest used methods was the use of a different color filter for each eye to separate pictures. Still later, polarization filters enabled even full color pictures to be seen separately by each eye. These were applied to motion pictures as well as to projected color slides. The major objection to these methods is that the viewer finds it distasteful and awkward to have any apparatus applied near or over his eyes, and as a result, these devices have not enjoyed great commercial success.
Later, somewhat useful devices were invented to avoid this problem by putting lenses at the picture, such as a series of strip pictures with prisms in front of them for advertising matchcovers or the now familiar 3-D picture postcards. Unfortunately, the application of this principle to large projected motion pictures or to home television receivers is extremely difficult, is seldom attempted and has not been commercially successful.
Recently, holography has produced relatively small 3-D pictures requiring no apparatus at the viewers' eyes. Unfortunately, the rest of the process is ill-adapted to either television or movie theaters and requires many inventions now beyond the state of the art. Also, certain aspects appear highly impractical, such as the probable requirement that each television station occupy tens or hundreds of times the space in the spectrum which it now uses, because of the enormous resolution requirements of holography. Even with such colossally economically difficult usage, much invention would be required, such as television receivers with dozens to hundreds of times present resolution and light valve rather than kinescope output to permit laser illumination to be used.
As for holography used for technicolor movies, this would require film of resolution dozens of times what is now used, and probably of gigantic size, unless gigantic light valves and screens are invented (with resolution related to the wavelength of light, not proportioned to screen size). Suffice it to say that the inventor of holography is known, through issued patents, to be working on the use of holography to produce a theater lens system on the screen (holography can do that), just once during theater or screen construction, and the lenses will then direct the light from one projector to the left eye of each person in the theater, and similarly for the right eye. Even this retreat from true holographic pictures to stereoscopic ones, using holography only to construct the initial lens system, is expected to be delicate and difficult.
In motion pictures, Cinerama and Cinemascope have achieved commercial success without stereoscopic or holographic means by projecting the picture around the sides of the observer so as to hide the edges, or at least the sides of the picture, and also to give the viewer something to see in his peripheral vision area. The invention to be described here achieves a similar effect, but does so without the difficulties of extra-wide film or projection, and perhaps more important, can be applied to color (or black and white) television and similar pictures whose subtended angle from the observer is limited and cannot, in any practical way, approach 90.degree. to 180.degree., as in the special movie theater adaptations of Cinerama and Cinemascope. Consider, for example, the staggering problem of a television screen or tube extending around the sides of the room to surround several observers. The economics of color television pictures gets rapidly out of practicality as one goes from 17 inches to only 30 inches, let alone room size.
The invention to be described here can produce the desired effect as an attachment on normal-sized TV tubes and effectively solves the economic and practical problem outlined in the preceding paragraph. Also, as one of its many other applications, it can make normal-sized movie screens and projection show appreciable depth effect.
What has been needed is an economical apparatus for use with single (not double or stereo) pictures of normal aspect ratio, which provides a depth or three-dimensional effect and works at or near the picture being viewed, so the viewer need not carry or wear any special viewing mechanism or aid, and need not change his normal optical habits or aids, such as his ordinary glasses.
An mentioned previously, the present invention makes a two-dimensional picture or image appear to be three-dimensional by suppressing or eliminating the clues by which an observer or viewer observes that a picture is two-dimensional, so that the viewer will react to other clues present in the picture, which then cause the eye-nerve network-brain mechanism to visualize depth.
A viewer generally observes a picture to be flat and two-dimensional in part because he can mentally locate the plane of the picture by seeing the edge of the picture, which binocular vision and focus judge very strongly and accurately; and in part by seeing the surface characteristics of the picture, such as gloss, texture, smudges, light reflections, and sometimes in television or old movies, noise spots or scratches all over the surface independent of the picture content. These surface characteristics can often be reduced to a negligible factor in practice, particularly in television and movies, and also in good photographs and some realistic or highly photographic paintings. Then it remains to effectively remove the picture edges from view and judgment to enable the many clues to depth contained within the picture itself to do their job of creating a three-dimensional image in the mind of the observer. It is important to note that simply covering the edges does not remove the edge barrier, since the edge of the cover constitutes a new edge, unless something special is done, as will be described later.
First, consider the various clues of both binocular and monocular types which the eye-nerve processing network and brain use to identify depth in a scene.
Two major binocular clues to depth are, the slight difference in angle from each eye to the object, perceived muscularly, and the differences in the picture perceived by each eye because of the distance separation between the eyes. The muscular perception clue is generally thought to be of small significance and disappears beyond a meter or so in distance. The different pictures, particularly the differences at obscuration edges are processed by nerve networks and brain to construct an ordered set of distances for the scene and is the major stereoscopic or binocular clue. An elaborate set of theories has been constructed about this concept, but they will not be described here since the present invention will be primarily avoiding this phenomenon rather than using it.
The invention will, however, be using many of the clues to depth which do not require the binocular interaction of two separated eyes. Some of these clues are:
1. The obscuration of distant objects by near ones.
2. The change in obscuration as a near object passes in front of more distant ones in movies or television, or in real life.
3. Judgments based on covergence with distance of presumed parallel lines, perspective, shape and relative size of well-known objects, and accurate angles and distances between lines heading for infinity and lines presumed to be accurately at right angles to them. These are powerful cues, and deliberate distortions of these have been used to produce many optical illusions.
4. Surface details of well-known objects as a function of distance.
5. Clarity variation with distance due to atmospheric contaminants or scattering, even in clear atmosphere.
6. Color variation with distance due to atmospheric absorption and scattering.
And, the last four to be named at this time:
7. The continuity of the peripheral scene from the observer's own head and shoulders clear around the walls and across the ground to the object.
8. The apparent motion of near objects opposite to observer's head motion, and far objects with head motion.
9. The variation in focus and depth of focus with the distance of an object (valid only out to ten meters or so, and not consciously observed because we keep refocussing all the time as we observe different parts of a scene).
10. The ability of the observer to modify what is being obscured, by moving himself, his head or his eyes, or by using one eye and then the other (often subconsciously).
With the exception of the last four, all of these monocular clues are present in a good color television or color moving picture, but the visible, well-defined edges or sides of the screen and hence the easy automatic ability to determine the screen's precise position in depth by the powerful binocular judgment of the edge, overwhelm the many monocular clues to depth in the picture which, for example, serve so well when one eye is closed to continue to produce a world view with obvious depth.
The literature has described devices to be used at the eye to eliminate the binocular clues which produce the sensation of flatness, and has described how such devices have produced a reasonable depth illusion from two-dimensional pictures. The present invention can produce an even better effect, and does so with apparatus only at the picture, not at the eyes. The effect can be better than that which was described in the literature because, in addition to using all the cues suggested there, we can use both eyes. Most importantly, we can add one cue of the last four with something not in the picture itself, and finally, we have available the advantage of motional obscuration variation within the picture itself if the invention is used on television or movies (both preferably but not necessarily colored).
Formal lists of methods to add depth to two-dimensional pictures in varying degrees of ease of effectiveness are given in two articles which are here quoted. These articles contain other references, sometimes in a foreign language and of earlier dates, but they claim to have summarized the earlier material.
One paper is "The Illusion of Depth from Single Pictures," Optical Society of America, Vol. 10, 1925, pp. 137-148, by A. Ames, Jr. He quotes the following ways of increasing the illusion of depth:
1. Looking at a picture with one eye only.
2. Looking at a picture through an iconoscope (a system of mirrors which effectively decreases the apparent distance between the eyes).
3. Viewing the picture from a great distance. (However, the obviously incorrect perspective usually counteracts the illusion, he says, and loss of surface detail probably also would spoil it.
4. Changing eye convergence via prisms.
5. Looking at a picture through a hole approximately 2mm in diameter held close to the eye. He says this upsets normal monocular depth perception by affecting the normal coordination between diffusion of the image and focusing of the eye. (This probably means it increases the depth of focus.)
6. Using one eye with a lens that changes normal viewing distance. This affects focus and changes perspective.
7. Using both eyes but with a lens such that one eye gets a sharp image and the other a blurred one. Blurring only in the horizontal direction is especially good using a cylindrical lens. The illusion is greater than with one eye alone and the reason is quoted as "hard to explain." (It suggests that the stereoscopic binocular brain processes are somehow involved.)
8. Looking at a picture in a mirror.
9. Looking at a picture with abnormal rotation of images about the axes of vision.
The second article, more closely related to the problem being approached here, is "Stereoscopic Depth from Single Pictures," by Harold Schlosberg, American Journal of Psychology, vol. 54, 1941, pp. 601-605. He quotes a number of ways in which flatness cues can be eliminated, permitting depth cues to yield a "plastic" or depth effect.
1. Looking at a picture from a distance.
2. Monocular viewing, (a) through a tube, (b) through a lens, and (c) in a mirror.
3. Partial binocular vision, (a) blurring one eye with a spherical or cylindrical lens, or (b) prisms.
4. With full binocular vision, through a large lens.
5. With mirrors to reduce the apparent separation of the eyes.
This author stresses the relatively "all or none" character of the effect. He states that we do not have a simple addition or subtraction of factors, with more or less depth resulting. He states that the plastic effect seems usually to be either clearly present or absent, although there may be some slight additive effects. In the use of the apparatus to be described, changes in the strength of the effect, particularly in the onset of the effect, with changes in parameters, have been seen.
The invention described herein differs from all of the suggestions in these articles in that it avoids doing anything at the eyes of the observer, but attempts to get as strong a dimensional illusion as any of these methods by working solely at or near the picture being viewed, thus releasing the viewer from carrying any mechanism or changing his normal optical habits or aids, such as ordinary glasses.
Now, in line with the suggestion in Schlosberg's article that looking down a tube will introduce depth perception in single pictures, it is suggested that the effect be tested by the reader as an example of an apparatus at the eye which produces the effect. Use a cardboard tube of approximately one and one-half inches in diameter and 6 to 12 inches in length, or if such is not available, roll up a magazine or report or even several sheets of letter paper to form a tube. Then look through it with one eye, the other kept closes, at, for example, a detailed colored picture which has some appreciable perspective or depth to the scene, while placing oneself at a distance such that the amount of picture shown by the tube opening is almost all of the picture, but the edges or sides of the picture are not visible. The effect is startling for most people.
Substantial solidity or depth sets in, which disappears and reappears as the tube is removed or used. If the picture is one taken from a high place looking down, some people feel strong visceral muscle tightening as in looking down from a height in the real world. This is particularly true when looking at color television or color movie scenes of this nature.
It is suggested that this viewing means be tried also with a good, clear, noise-free picture on a color television receiver and at the movies. The effects are often shocking and visceral. Color commercials, particularly, take on great depth and when zoomed appear to physically rush at or away from the observer by many feet, and may even cause him to duck away from the oncoming object. In movies, complex scenes such as battles or panoramic activities become clearer because of the added dimensionality. Interestingly, especially in TV, full screen heads or hands moving take on strong dimensionality, because of the strong effects of perspective.
It appears that the more often one sees the effects, the stronger and more general they become; apparently the brain quickly trains itself to believe this new mode of viewing. However, almost always the effect is there to a marked degree at the first viewing of an appropriate picture. Chase scenes or daredevil scenes (hanging from a bridge or a window, etc.) become viscerally affecting, and in sports, it becomes far easier to follow the action.
Beyond what the inventor learned from the articles by Schlosberg and Ames previously quoted, he soon found that the use of both eyes, if they look through separate tubes or through a single tube, did not remove the effect, but actually enhanced it, as long as the picture edges or sides were still hidden by the sides of the viewing tubes. This was an unexpected and highly gratifying result, since it suggested that it would be worth while to seek an equivalent device to the tube or tubes at the eyes, which would be at the picture, and that the use of both eyes might not prevent it from working.
At this point in his understanding, the present inventor began experimenting with various attachments to a color television receiver in an attempt to duplicate the effect seen looking down a tube or tubes without having the observer put anything at or near his eyes.
The first experiment was to make a tunnel-like structure of a black cardboard tube, just the size of the picture, or a little smaller, ending sharply on the glass of the picture tube. Surprisingly, this has a relatively minimal effect, if any. What effect there was, may have been caused by the greater contrast available, since the surface of the picture tube was shielded from appreciable extraneous light. The place at which the black cardboard tube ended on the picture tube was sharp and clearly evident and identified the true plane of the picture when looked at normally with two eyes.
Variations were tried, such as having the opening of the cardboard structure toward the observer made smaller than the picture visible area and looking into this limited angle viewing system from the front. This worked poorly, if at all, for depth enhancement.
Then an experiment was made using a rectangular aperture slightly smaller than the color picture, with all four sides consisting of cylinders disposed around the margin of the picture so that the rounded or curved edge which limited the view of the picture tube was closer to the observer than the plane of the picture tube glass, by about one-fifth of a picture diameter. Also, these cylinders hid the edges of the picture tube, so the distance to the plane of the picture was difficult to judge. This produced the depth effect.
Next, following practice in movie theater screen construction or in normal TV masks or bezels, cylinders were tried using dull black light-absorbent material which was almost invisible in a dimly lit room, with the prospect of later going to black velvet, if necessary. This appeared to be in a wrong direction, since all that could be seen from a distance was the picture tube with a sharp, well-defined edge and slight but rather poor depth enhancement.
Next, moderately dark colored cylinders of a dull material were used and a good effect of depth returned, suggesting that the viewing aperture should be moderately visible (extremely bright or bright-colored apertures were found to diminish the effect) and some distance in front of the surface of the glass (typically 5 percent to 30 percent of a picture width). It was essential that the picture be larger than the aperture, and the aperture be spaced out in front of the picture such that the observer's head or eye movements cause greater or lesser amounts of the scene to be revealed, just as when looking out of a window. Even without movement, the right and left eyes see a slightly different amount of picture near the side aperture edges.
To increase the effect of being unable to determine how far the picture tube surface was behind the clearly determinable aperture-producing mechanism, regularity such as a completely cylindrical cross-sectional shape for the edges of the frame or hood is generally to be avoided and hoods of other shapes were tried, with great success. Nevertheless, the effect is strong enough that such cylindrical cross-sectional edges do work, to a degree. As an example of radically different shapes which were tried, a drapery extending outward from the glass surface was used with the limiting aperture provided by folds of the drape well removed from the picture tube surface. Colored, moderately visible drapes work substantially better than black ones.
Looking at the picture produced by draping or other good mask arrangements made in accordance with the principles of the present invention produces a depth effect which does not improve substantially if the picture is looked at through a cardboard tube used at the eye. In fact, this is a good test as to whether or not the principles of the present invention have been properly utilized. If the parameters are not close to their optimum values, as will be described, looking at the picture through a tube at the eye shows a much greater depth than is produced by the apparatus at the screen. When these elements are properly held at values described here as near optimum, little or no change is observed as between a tube at the eye or the use of apparatus at the screen. It appears that the present invention gets essentially all the effect obtainable from removing binocular clues as measured by use of the monocular tube.
The invention also has application to the showing of black and white or color slides and movies. Black and white television is also materially enhanced by this concept, but not quite as strongly as color. For movies and slides, rear projection is the most obvious parallel to picture tube technique, although front projection is not ruled out if projected picture edges are carefully controlled and do not show appreciably on the draping. The black matte frame technique normally used in movie theaters to control the picture edge problem is wrong for this depth perception and gives an apparent sharp edge right at the screen plane, which kills the effect. Testing with a tube at the eye shows great depth enhancement, which indicates how little depth effect normal theater technique is providing.
Similarly, all of the elaborate picture tube frames or bezels used on commercial television receivers may be observed to leave the picture edge in clear view at an easily judged distance, and they do not show the depth enhancement which emerges at the moment the teaching of this invention is utilized. It seems clear that current designers are not aware of these principles and it is in no way intuitive or obvious to persons skilled in the television receiver art that these principles would add depth to their designs. Similarly, when it has been shown to persons skilled in the television art that depth enhancement can be obtained by looking down a tube and suggested that this might be obtainable from a properly designed mask at the tube, their guess is generally a black matte mask, as in common movie technique. This does not work on television, just as it does not work in movies to provide the depth enhancement described here. Again, it is clear that the correct approach described here is not obvious to these practitioners of television design. Over the many years of movie theater and television receiver design, they have not only used schemes which do not show the depth enhancement effect; when shown the effect via a tube at the eye, they guess wrong as to what would work at the screen.